Present perfect tence vs. Past tense

Professional writing services offer writing help to anyone. Using the services of professional writing company will help you answer questions such as why is the present perfect tense commonly used in the "since" clause instead of the past tense.

To answer the question better, let us first identify the keywords. The present perfect tense denotes a completed action/condition with an indefinite time or an action/condition that is continuing in the present. On the other hand, “since” is a conjunction for a subordinate clause while past tense indicates a completed action or condition. Both the present perfect tense and the past tense are a form of verb which expresses actions or conditions beginning in the past.

In the sentence "It's been a long time since I've seen her", present perfect was used because there was no definite time indicated. Present perfect tense is used when the action was something that was done repeatedly or habitually that has not been done for "a long time". Using the past tense would suggest a one-time event such as "It's been a long time since I saw her", which would mean that the speaker saw "her" once or a few times long ago.

However, the sentence may also denote that the speaker habitually saw the person before but some time has passed since then. A simpler explanation would be that, as said above, present perfect tense also denotes an action/condition that is continuing in the present. The word "since" is also used to talk about an action that started in the past and is continuous up to now. Hence, the present perfect tense is what is commonly used by many.